Novel technique for the combined recovery, extraction and clean-up of forensic organic and inorganic trace explosives samples.

This paper describes a simple processing and analysis scheme for explosives trace swab samples which deals both with organic and inorganic materials. Swabs, wetted with ethanol or ethanol/water mixture, were extracted with ethanol/water mixture. The extract was passed directly through a simple column containing an acrylonitrile/styrene copolymer adsorbent. The adsorbent retained common organic explosives, which were recovered with an efficiency of 30-50% as a relatively clean ethyl acetate solution. The concentrated ethyl acetate eluate was analysed using gas chromatography with chemiluminescence or mass spectrometric detection. The unretained inorganic ions and sugars, which were recovered with generally high efficiency as an ethanol/water solution, could be directly analysed using ion chromatography and/or capillary electrophoresis. Minor difficulties encountered in the analysis of sugars, fluoride and phosphate were examined.     

血液中乙醇保存稳定性研究

目的确定血液中乙醇最佳保存条件,探讨影响血液中乙醇含量稳定性的主要因素。方法对血液保存的温度(-20、4、20℃)、防腐剂(NaF、无防腐剂、Na2O2)、储存容器中空气所占比例(0%、25%、50%)和血醇质量浓度(0.2、0.8、2.0mg/mL)四个因素采用正交试验L9(34)方法分组,样本采用顶空气相色谱法进行测定,测定结果采用方差分析进行讨论。结果在20℃保存且不加入防腐剂的两组样本中血醇浓度变化明显,其余变化不明显。结论血液样本在4℃、储存容器中空气比例为50%和加防腐剂(NaF)的条件下保存,稳定性最佳;四个影响因素中温度为影响血液中乙醇含量稳定性的主要因素。     

Characterisation of gunshot residue from three ammunition types using suppressed anion exchange chromatography

Gunshot residue (GSR) is commonly analysed in forensic casework using either scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX) or gas chromatography-mass spectrometry (GC-MS). Relatively little work has been reported on the post-discharge GSR content of non-metallic inorganic or low molecular weight organic anions to distinguish between different ammunition types. The development of an analytical method using suppressed micro-bore anion exchange chromatography (IC) is presented for the analysis of GSR. A hydroxide gradient was optimised for the separation of 19 forensically relevant organic and inorganic anions in <23min and sensitivities of the order of 0.12-3.52ng of anion detected for all species were achieved. Along with an optimised extraction procedure, this method was applied to the analysis of post-ignition residues from three selected ammunition types. By profiling and comparing the anionic content in each ammunition residue, the possibility to distinguish between each type using their anionic profiles and absolute weight is presented. The potential for interference is also discussed with respect to sample types which are typically problematic in the analysis of GSR using SEM-EDX and GC-MS. To the best of our knowledge this represents the first study on the analysis of inorganic anions in GSR using suppressed ion chromatography.     

A Comparison of Solvent Extract Cleanup Procedures in the Analysis of Organic Explosives

The use of an organic solvent to extract explosive residues from hand swabs and postblast debris inevitably leads to the coextraction of unwanted materials, usually in far greater quantities than any explosive residue. In this study, the extraction efficiency of a number of solvent cleanup procedures including solid‐phase extraction (SPE), adsorbent resins such as Chromosorb‐104, and traditional materials such as silica and Florisil was calculated using a quantitative liquid chromatography–ultraviolet (LC‐UV) detection procedure. The Oasis^® HLB cartridge outperformed other cleanup procedures, with analyte recoveries approaching 95%, while the Amberlite XAD‐7 procedure returned the lowest overall recoveries. The matrix rejection ability of each method was then determined using a simulated highly contaminated matrix, with the adsorbent resins showing a higher degree of matrix rejection, which is seen as a reduction in background noise in the UV chromatogram using 210 nm detection.     

Combined Collection and Analysis of Inorganic and Organic Gunshot Residues

Gunshot residue (GSR) analysis and their interpretation provide crucial information on a criminal investigation involving the use of firearms. To date, several approaches have been proposed for the implementation of a combined sampling and analysis of inorganic (IGSR) and organic GSR (OGSR). However, it is not clear at this stage if concurrent analyses of both types of residue might be detrimental to the analysis of IGSR currently applied in forensic laboratories. Thus, this work aims to compare and evaluate three different protocols for the combined collection and analysis of IGSR and OGSR. These methods, respectively, involve the use of a modified stub (with two halves, one for the detection of IGSR and the other for the analysis of OGSR); the sequential recovery of GSR with two stubs mounted with different adhesives (double-sided carbon tape and Tesa® TACK) and the sequential analysis of IGSR and OGSR from a single carbon stub following carbon deposition. The detection of IGSR was carried out using SEM-EDX, while OGSR analysis was performed using ultra-high-performance liquid chromatography–tandem mass spectrometry (UHPLC-MS/MS). Obtained results for experiments performed using Geco Sinoxid^® ammunition indicated that sequential analysis was the most suitable protocol for the combined collection and analysis of both IGSR and OGSR. A higher number of inorganic (characteristic and consistent) particles and higher concentrations of ethylcentralite, N-nitrosodiphenylamine, diphenylamine, and nitroglycerin were recovered with this method.     

Evaluation of different sampling media for their potential use as a combined swab for the collection of both organic and inorganic explosive residues

Commercially available skin cleansing alcohol wipes and conventional swabs were investigated for their use as a universal sampling medium for the simultaneous collection of both organic and inorganic explosive residues. Six compounds with the potential to be encountered in casework [pentaerythritol tetranitrate (PETN), 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), triacetone triperoxide (TATP), ammonium nitrate, and sodium chlorate] were selected as representative target compounds. Quantities of these target compounds were deposited on four different substrates (glass, plastic, aluminium foil and laminate). Two chosen alcohol wipes demonstrated better overall performance in the recovery of both the organic and inorganic representative compounds from each of the test surfaces compared to the results obtained using conventional cotton and polyester swabs, pre-moistened with various solvents, and a direct methanol wash (used as a control). Results obtained using dry cotton swabs indicated that it was not an effective swabbing system for the collection of both organic and inorganic explosive residues on common substrates.     

Discriminating Hodgdon Pyrodex® and Triple Seven® Using Gas Chromatography–Mass Spectrometry

Abstract: Pyrodex ^® and Triple Seven ^® are black powder substitutes that often find use as fillers in improvised explosive devices, such as pipe bombs. These propellants have essentially the same overall appearance and oxidizers, but different fuels. For example, Pyrodex ^® contains sulfur, sodium benzoate, and dicyandiamide (DCDA), whereas Triple Seven ^® lacks sulfur but also contains 3‐nitrobenzoic acid. In this method, intact particles and postblast solid residues were reacted with bis(trimethylsilyl)trifluoroacetamide + 1% trimethylchlorosilane in acetonitrile for 30 min at 60°C. The resultant trimethylsilyl derivatives of the organic fuels were then analyzed by gas chromatography–mass spectrometry. Each derivative was clearly resolved from other components, and high‐quality mass spectra were obtained. In addition, characteristic fragments resulting from loss of a methyl radical from the molecular ion (m/z 163 for sulfur, m/z 171 for DCDA, m/z 179 for benzoic acid, and m/z 224 for nitrobenzoic acid) were able to be monitored.     

Analysis of hydrogen peroxide field samples by HPLC/FD and HPLC/ED in DC mode

The goal of this paper is to describe applications of two recently developed HPLC methods for the analysis and confirmation of the presence of hydrogen peroxide residues in field studies. The procedure utilizes two different HPLC systems, one with post-column derivatization followed by fluorescence detection (HPLC/FD), and the other with electrochemical detection (HPLC/ED). The two systems were utilized to detect hydrogen peroxide in a variety of typical forensic samples including pre- and post-blast samples, as well as a series of environmental control samples. Peroxide-based organic explosives were also examined due to their propensity to produce peroxide residues following detonation. Because samples collected from post-blast scenes are frequently shipped or stored prior to analysis, the effects of storage time, temperature and type of substrate material on the recovery of hydrogen peroxide residues were also investigated. The combined results of the study demonstrate the capability of two HPLC approaches with selective detection in the analysis and investigation of suspected incidents involving peroxide based explosives.     

Application of LC−QTOF/MS for the validation and determination of organic explosive residues on Ionscan® swabs

The identification and confirmation of trace explosive residues along with potential precursors and degradation products require a comprehensive laboratory analysis procedure. This study presents the determination of organic explosives consisting of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), 2,4,6-trinitrotoluene (TNT), 2,4,6,N-tetranitro-N-methylaniline (Tetryl), 1,3,5-trinitrobenzene (1,3,5-TNB) and pentaerythritol tetranitrate (PETN) by a high-resolution liquid chromatography quadrupole time-of-flight mass spectrometry (LC−QTOF/MS). The qualitative information including retention time, collision energy, precursor ions, and characteristic fragmentation pattern of each explosive were collected using an atmospheric pressure chemical ionization (APCI) in negative ion mode. The separation efficiency among five compounds was greatly achieved in this study. Four real explosive samples consisting of TNT, RDX, PETN and Tetryl and 12 Ionscan® quality control swabs from the Royal Thai Army were also tested to validate and verify the viability of the GC–MS method used to validate results from an Ionscan® system. The results showed that LC−QTOF/MS is a powerful technique for the identification and confirmation of thermally unstable organic explosives on Ionscan® swabs compared to a conventional GC−MS technique.     

离子色谱法检测全血中的亚硝酸盐及其代谢产物

目的建立全血中亚硝酸盐的离子色谱分析方法。方法将0.5mL全血和1mL水混合,用乙腈沉淀血液中的蛋白质后依次过C18柱、Ag柱和Na柱,用于去除其中的有机物和氯离子后进行离子色谱检测,并对蛋白沉淀溶剂、前处理柱等最佳实验条件进行考察。结果采用本文方法对空白添加全血进行检测,在色谱图上亚硝酸根离子及其氧化产物硝酸根离子的保留时间分别为10.02min、19.21min。选择乙腈作为蛋白沉淀剂,C18柱去除有机物,Ag柱去除氯离子,Na柱去除银离子。全血中亚硝酸根离子的检出限为0.05μg/mL,亚硝酸根和硝酸根的总回收率为95.9%~117.3%。结论本文方法简便,回收率好,灵敏度高,适用于中毒者血液中亚硝酸盐的检测。     

肝中对硫磷的固相萃取—电子捕获检测气相色谱分析法

目的建立肝中对硫磷的快速、灵敏、可靠的GC／ECD分析方法。方法肝匀浆加内标甲基对硫磷,用乙腈浸提,浸提液加6％高氯酸稀释,稀释的上清液用GDX403树脂进行固相提取,提取物用HP-5色谱柱和电子捕获检测器进行气相色谱分析。结果提取率92.3％,检测限7.8ng／g,线性范围0.04～4.0μg／g,回收率99.6％±6.2％(Mean±CV,n=5)。结论方法简便、灵敏适合于实际案件检验。     

Testing Antemortem Blood for Ethanol Concentration from a Blood Kit in a Refrigerator Fire

The stability of ethanol in antemortem blood stored under various conditions has been widely studied. Antemortem blood samples stored at refrigerated temperature, at room temperature, and at elevated temperatures tend to decrease in ethanol concentration with storage. It appears that the stability of ethanol in blood exposed to temperatures greater than 38°C has not been evaluated. The case presented here involves comparison of breath test results with subsequent analysis of blood drawn at the time of breath testing. However, the blood tubes were in a refrigerator fire followed by refrigerated storage for 5 months prior to analysis by headspace gas chromatography. The subject’s breath was tested twice using an Intoxilyzer 8000. The subject’s blood was tested in duplicate using an Agilent headspace gas chromatograph. The measured breath ethanol concentration was 0.103 g/210 L and 0.092 g/210 L. The measured blood ethanol concentration was 0.0932 g/dL for both samples analyzed. Although the mean blood test result was slightly lower than the mean breath test result, the mean breath test result was within the estimated uncertainty of the mean blood test result. Even under the extreme conditions of the blood kit being in a refrigerator fire, the measured blood ethanol content agreed well with the paired breath ethanol test.     

自制海洛因标准品在常用有机溶剂中稳定性研究

目的 研发海洛因标准品及优化分析方法,以对云南缴获海洛因样本提纯制备成的自制海洛因对照品在常用有机溶剂中的稳定性进一步研究.方法 采用内标及GC、GC/MS方法,通过对提纯制备的海洛因在5种有机溶剂中冷藏保存后含量的变化,观察海洛因在常用有机溶剂中的稳定性.结果 乙醇、三氯甲烷及乙腈为溶剂的自制海洛因对照品储备液,保存30天时间范围内海洛因含量未发生明显变化;以丙酮作为溶剂的自制海洛因对照品储备液,在7至30天时间范围内,海洛因含量明显升高;以甲醇作为溶剂的自制海洛因对照品储备液,在0小时至30天时间范围内,海洛因含量一直呈明显的下降趋势.结论 乙醇、三氯甲烷及乙腈可以作为海洛因样品储备液溶剂使用,丙酮、甲醇不适合作为海洛因样品储备液溶剂使用.     

Transfer of nitroglycerine to hands during contact with commercial explosives

The techniques of thin-layer chromatography, gas chromatography with electron capture detection, and gas chromatography/mass spectrometry were used to analyze hand swab extracts for the presence of nitroglycerine. Both the amount of nitroglycerine transferred to the hands after handling commercial explosives and its persistence were measured. Gas chromatography-electron capture detection was found to be the most accurate and sensitive technique for making such determinations, especially if the extract was partially purified by thin-layer chromatography prior to analysis. The lowest limit of detection was 10 ng of nitroglycerine, and residues could be detected over 20 h after handling the raw explosive.     

Effect of swabbing technique and duration on forensic DNA recovery

Various factors have been shown to affect performance of the conventional wet-dry double and single wet swabbing techniques to recover DNA, such as pressure and angle of application, volume and type of wetting agent, and swab type. However, casework laboratories in some jurisdictions have recently adopted different swabbing techniques that include wet-moist double swabbing and moist-dry single swabbing. Factors affecting the effectiveness of these recent techniques in maximising DNA recovery therefore need to be investigated. Here, the performance of traditional and recent swabbing techniques was compared and the impact of swabbing duration on DNA recovery was investigated. Ten µl aliquots of a known concentration of DNA extracted from human blood were deposited on pre-cleaned DNA-free cotton swatches (porous) and porcelain tiles (non-porous). Five swabbing techniques were used, of which three were double swabbing techniques: wet-moist, wet-wet and wet-dry, and two were single swabbing techniques: wet and moist-dry. For a ‘wet’ or ‘moist’ swab, 100 or 50 µL water was added, respectively. For a moist-dry swab, water was applied to one side of the swab, leaving the other side drier. Each swabbing technique was applied for two durations, 15 and 30 s per swab, with 5 reps of each combination (n = 100 plus controls). All samples were extracted and quantified, and a sub-set was profiled. The results showed that the wet-moist double swabbing technique with a swabbing duration of 30 s maximised DNA recovery from cotton. From tile, a single wet or moist-dry swab maximised DNA recovery, but increasing swabbing duration from 15 to 30 s had no impact. These data can be used to inform standardisation of DNA collection protocols across casework laboratories.     

Comparison of Different Swabs for Sampling Inorganic Gunshot Residue from Gunshot Wounds: Applicability and Reliability for the Determination of Firing Distance

This study concentrates on samples of bare pork skin, with and without bristles, and dried bovine ribs shot with a semi‐automatic pistol to find the best methodology and sampling surface in the search for inorganic gunshot residues (IGSR). Four quadrants of known surface areas were sampled at different distances from the bullet's hole with different swabs: tapes in graphite, Leukosilk® white tape, 3M® transparent tape, and a cotton swab to assess the technique able to collect the highest amounts of IGSR with the lowest contribution of the blank. The cotton swab wet in 10% HNO₃ gave the best results. The highest amounts of IGSR, measured by ICP‐OES and MS, were detected on a surface of 3‐cm radius from the bullet's edge. The amount of metals collected decreased with the firing distance between 20 and 60 cm. The procedure was efficient for sampling different tissues like skin and bones.     

Extraction of trifluralin from acetonitrile solutions

Results of extraction of trifluralin from an aqueous acetonitrile solution using various organic solvents are presented. The degree of extraction was shown to depend on the nature of extractant and the water/acetonitrile ratio. An optimal electrolyte and the degree of saturation of the water-acetonitrile layer with this electrolyte were selected. The highest efficiency of extraction was achieved by using water-saturated ethylacetate as an extractant. The indices of extraction were calculated as necessary for the isolation of a given amount of trifluralin from aqueous acetonitrile (4:1) solutions with the solvents considered in the present study.     

Swabs as DNA Collection Devices for Sampling Different Biological Materials from Different Substrates

Currently, there is a variety of swabs for collection of biological evidence from crime scenes, but their comparative efficiency is unknown. Here, we report the results of an investigation into the efficiency of different swab types to collect blood, saliva and touch DNA from a range of substrates. The efficiency of extracting blood and saliva from each swab type was also tested. Some swabs were significantly more effective than others for sampling biological materials from different substrates. Swabs with the highest sampling efficiency, however, often did not have the highest extraction efficiency. Observations were recorded regarding practicality of each swab in a variety of situations. Our study demonstrates that selection of sampling device impacts greatly upon successful collection and extraction of DNA. We present guidelines to assist in evaluation of swab choice.     

HS-GC内标曲线法测定血中乙醇含量的不确定度评估

目的建立自动顶空-气相色谱(HS-GC)内标曲线法测定血中乙醇含量的不确定评估方法。方法从分析测定程序着手,依据不确定度评定的指导性文件,分析不确定度来源,量化不确定度分量,计算检测结果的合成标准不确定度和扩展不确定度。结果各相对不确定度来自于检材重复性检测为3.4%,乙醇标准溶液为0.71%,检材为0.61%,叔丁醇内标溶液为0.41%,标准曲线为1.1%,气相色谱仪为1.3%,血液中乙醇的相对扩展不确定度为3.9%。结论血液中乙醇含量的不确定度主要来源于检材重复性检测、气相色谱仪、乙醇标准曲线。     

Methods used for the killing and preservation of blowfly larvae, and their effect on post-mortem larval length

A record of the length of the largest larvae collected from a corpse can be used to estimate the age of the oldest larvae present and, therefore, give an estimate of minimum time since death. Consequently, factors that affect post-mortem larval length will impact on any estimate of PMI based on it. Methods used to kill and preserve larvae are known to affect post-mortem length. This study looks at the effects of different preservatives, and variations in the protocol used for killing larvae by immersion in a hot water bath = [hot water killed; HWK], on the length of dead larvae of two common blowfly species. Post-feeding third instar Calliphora vomitoria and Lucilia sericata larvae were either HWK in boiling water and then placed in 80% ethanol or 10% formaldehyde solution, or placed live into the preservatives. For both species, choice of preservative and method of killing significantly affected post-mortem length. There were significant interspecific differences in their response to identical methods of killing and preservation. Additional experiments were carried out where C. vomitoria larvae were HWK in water at 80 and 100 degrees C for 1, 30, 60 and 90 s duration. Both temperature and duration significantly affected post-mortem length. Maximum length was attained after at least 60 s immersion. The amount of post-mortem decomposition that occurred after the larvae were placed in preservative could be greatly reduced by increasing the duration of immersion and/or increasing the water temperature. For the HWK larvae, it was possible to record their length immediately after death and before they had been placed in preservative. This data revealed that where 80% ethanol was used as a preservative the larvae expanded in the preservative. The timing of this expansion was investigated with a sample of C. vomitoria, HWK at 100 degrees C for 30 s and recording post-mortem length immediately after death and again after 3, 6, 9, 12, 24, 27, 30 and 33 h storage in 80% ethanol. Maximum length was recorded after 12 h storage and the rate of expansion was highest during the first 3 h in this preservative. After long-term storage (290 days), larvae killed and preserved in the same way were on average 0.7% longer than immediately after death and 0.6% (0.11 mm) smaller than when last measured (after 28 days storage).